1. Field of the Invention
This invention relates to optical apparatus for correcting optical distortion in an imaging system. More particularly this invention relates to an imaging system wherein an optical assembly compensates for geometric incompatibility between the formatted output of a video sensor and a line monitor.
2. Description of the Prior Art
In endoscopic and related video systems it is common practice to employ single chip charge coupled devices (CCD) for image acquisition. The predominant video convention in the United States has long been NTSC, employing 525 scan lines, and it is the usual manufacturing practice to construct the CCD in a specific pixel format, for example 510 pixels per horizontal line and 488 horizontal lines. The format varies widely. 480 horizontal lines are known, as are formats employing 768 pixels per horizontal line. When the output of such a CCD device is coupled to suitable video processing electronics, the resulting composite signal accommodates the NTSC monitor screen. In other parts of the world different video conventions are employed, for example, the European PAL convention having an identical aspect ratio, but having 625 scan lines. Accommodating a 625 line PAL monitor would ideally require a CCD device having about 588 horizontal lines. A need exists in the art for utilizing existing single chip NTSC compatible CCDs with PAL and other non-NTSC monitors to avoid the expense of redesigning the CCD chip. As used herein, the terms "NTSC" AND "PAL" refer to the U.S. 525 line and the European 625 line color systems respectively, rather to the color modulation standards alone.